With advance of higher reliability of print output in word processors, for instance, the number of dots which constitute a character pattern has been increased rapidly. Therefore, there arises a problem in that the capacity of a character generator memory for storing characters as dot pattern data increases more and more.
To overcome the problem as described above, a so-called outline font method has been proposed such that the outline of a character pattern is divided into a plurality of areas j0, j1, j2, . . . as shown in FIG. 1, for instance; the start and end point coordinates of these areas j0, j1, j2 . . . are previously stored as data; and the divided outlines are interpolated on the basis of dot signals before output.
In this method, since not only high reliable characters of many dots can be outputted in spite of a relatively small amount of data to be stored, but also the character sizes can be expanded and contracted by coordinate calculation, there exists an advantage of coping with characters of various sizes.
However, since the outline information as described above can be obtained by approximating a curve J for forming a character outline as shown in FIG. 2A on the basis of straight lines K, K and a circular arc L as shown in FIG. 2B, when the curve is required to be approximated precisely in particular, there exists a problem in that a great number of circular arcs of different radii must be stored so that the memory capacity inevitably increases.
To overcome the above-mentioned problem, there has been proposed another method of approximating the character outline by use of Conic-spline or Bezier function which can determine a curve on the basis of three points of start and end points A and B of a curve representing an outline and a control point C indicative of an intersection of two tangent lines described at these points A and B as shown in FIG. 2C. When the Conic-spline or Bezier function is adopted, it is possible to approximate the character outline by a smooth curve in spite of a relatively small memory capacity.
In the prior-art character pattern signal generating systems, however, dot signals corresponding to a character pattern are generated through complicated processing such as conversion into outline information described by only straight lines, conversion into outline data composed of dot signals on dot coordinates, etc. Therefore, there exists a problem in that a great amount of memory capacity is required, because the outline information composed of dot signals must be temporarily stored in some memory medium in the process of forming the outline information composed of dot signals on the basis of outline data described by an approximate function and the process of forming dot signals corresponding to the character pattern on the basis of the outline information composed of dot signals.